The present invention relates generally to a steering assembly for automotive vehicles, and more particularly to a rack and pinion steering mechanism.
An important requirement for automotive steering mechanisms, particularly rack and pinion power-assisted mechanisms, is offering stable steering means with precise movement between a pinion and a rack bar. This may be accomplished by mounting the pinion and the rack bar within established limits of tolerance in order to provide proper contact points between the gear section of the pinion and the gear section of the rack bar. Sometimes, however, the tolerances vary beyond the established limits and create excessive clearances between the respective gear sections. The correction commonly involves additional complicated and time-consuming operations.
Moreover, the pinion gear section and the rack bar gear section are subject to wear over the life of the vehicle. Wear may be caused by axial stresses that urge the rack into a position distant from, and out of proper assembly with, the pinion. These stresses create a force opposed to maintaining the pinion and rack bar teeth in proper engagement. This wear may create undesirable noise and improper alignment of steering wheel relative to the vehicle.
A first type of correction for improper alignment is manual correction that occurs only during certain periods, such as during the initial vehicle assembly and periodic maintenance.
One such device for manual correction holds the pinion in place with a roller bearing and applies a force to the rack bar with a spring. The spring and the roller bearing combine to urge the pinion and rack bar together into a proper assembled relationship. However, this type of adjustment is mechanically complicated and may be imprecise and costly, both during manufacturing and during servicing of the motor vehicle. Further, the spring may be subject to fatigue.
Another such device for manual correction employs a bushing that is selectively rotatable and eccentric with respect to the pinion. As the bushing is manually rotated, the bushing adjusts the position of the pinion with respect to the rack. The bushing is typically only rotated during periods of manual adjustment, such as during the initial assembly or during periodic maintenance of the steering mechanism. Furthermore, the bushing typically includes a locking mechanism that prevents rotation of the bushing when the rack and pinion assembly is not being aligned.
A second type of correction for improper alignment is automatic correction. Automatic correction may occur during operation of the steering assembly, typically while the vehicle is in operation.
One such device for automatic correction includes a spring-loaded yoke applying a constant force to the rack and pinion and, therefore, urging the two components together. However, this type of adjustment is mechanically complicated and may be imprecise and costly, both during manufacturing and during servicing of the motor vehicle. The spring may additionally be subject to fatigue. Furthermore, if this automatic adjustment device is employed with a manual automatic adjustment device, the spring may become radially misaligned during the manual adjustment. More specifically, if the manual adjustment device is rotated, the automatic adjustment device typically likewise rotates, thereby applying an undesirable force between the rack and the pinion.
It is therefore desirous to improve the relationship between the gear sets of the rack and pinion steering mechanism with simplified manual and automatic support devices that substantially avoid misalignment.